Draw-out fused switch-gear apparatus



P 20, 1966 J. E. GODFREY DRAW-OUT FUSED SWITCH-GEAR APPARATUS Filed March 1, 1965 5 Sheets-Sheet 1 m W A E V W L/. [Dw/N GODFREY #1 Wit A TTOANEY Sept. 20, 1966 J. E. GODFREY DRAW-OUT FUSED SWITCH-GEAR APPARATUS 5 Sheets-Sheet Filed March 1, 1965 INVENTOR. d [aw/N Goomzv BY KMJ-C Sept. 20, 1966 J. E. GODFREY 3,274,356

DRAW-OUT FUSED SWITCH-GEAR APPARATUS Filed March 1, 1965 5 Sheets-Sheet 5 INSULATION} INSULATION INVENTOR. 4 [DW/A/ GODFREY ATTORNEY United States Patent York Filed Mar. 1, 1965, Ser. No. 435,876 5 Claims. (Cl. 200-114) This invention is related to a draw-out switch-gear apparatus, and more particularly to such apparatus which is especially adapted to be removably engageable with fixed electrical connectors connected to a source of electrical energy and to an electrical load. A particular feature of the present invention is the arrangement by which appropriate switch means connectable in circuit with the draw-out switch-gear apparatus is removably mounted upon that portion of the apparatus which may be selectively withdrawn from electric-a1 engagement with the aforementioned electrical source and electrical load connectors.

A principal object of the present invention is to provide a draw-out switch-gear apparatus in which the switch means connected in circuit in such apparatus may be readily removed as desired.

Another object of the present invention is to provide such a draw-out switch-gear apparatus employing a circuit breaker as the switch means connected in circuit with the apparatus and providing that the circuit breaker may be easily and readily removed from its normal mounted position for replacement, repair, calibration, or test.

Another object of the present invention is to provide such a draw-out switch-gear apparatus incorporating current limiting means. i A further object of the present invention is to provide a draw-out switch-gear apparatus having a circuit breaker connected in circuit with the aforementioned current limiting means which circuit breaker may be automatically operable to interrupt the flow of overload currents or manually operable to interrupt the flow of currents therethrough before the switch-gear apparatus is withdrawn from electrical engagement with the electrical source connectors andelectr-ical load connectors.

A still further object of the present invention is to provide such a draw-out switch-gear apparatus which is compact, simple, and of extremely durable construction.

The invention in one form may comprise a frame assembly including front and rear insulating walls aligned in generally parallel relationship and spaced from each other. The front and rear insulating walls have connected therebetween a plurality of fusible means disposed generally in spaced, horizontal alignment. Also supported in connection between the front and rear insulating walls of the frame assembly are a plurality of electrical conductors. Both the electrical conductors and fusible means are in electrical engagement with electrical connectors which pass through the front insulating wall; a like plurality of electrical connectors are arranged in electrical engagement with both the fusible means and the electrical conductors, respectively, and pass through the rear insulating walls. The electrical connectors passing through the rear insulating wall are arranged to be removably engageable in electrical contact with a like plurality of electrical connectors fixedly supported on a support structure. Suchfixed electrical connectors may preferably take the form-of the so-oalled tulip-type connectors and are arranged to be connected to an elec trical source and an electrical load.

The electrical connectors which are aligned horizontally and pass through the front insulating wall are so spaced and disposed as to afford a means for removable electrical engagement with a switch means such as a circuit breaker, for instance, connected in series electrical I 3,274,356 Patented Sept. 20, 1966 engagement to complete multi-pole circuits from the electrical source to the electrical load. The front insulating wall is also arranged to support a trim plate thereon to cover and protect the switch means and provide a suitable handle pull means for withdrawal of the frame assembly which forms the removable portion of the switch-gear apparatus. The trim plate has an aperture therein adapted to allow the externally extending, reciprocally operable handle of the circuit breaker or like switch means to pass therethrough. The front and the rear insulating walls, the fusible means and electrical connectors therebetween, the circuit breaker or switch means mounted on the front insulating wall, and the trim plate supported by the front insulating wall are supported by a suitable rail means secured to the front and rear insulating walls. One such rail is disposed on either side of the frame assembly and the rails are adapted to be received slidingly within rails of the fixed support structure, the rail arrangement being disposed to afford the alignment of the electrical connectors on the rear insulating walls for sliding engagement and electrical contact with the fixed connectors supported and mounted on the support structure by sliding the entire frame assembly along the rails to such engagement.

These and other objects and features of the present invention will be more fully understood from the following detailed description together with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawings:

FIGURE 1 is an exploded perspective view of an embodiment of the present invention;

FIGURE 2 is a perspective view of the embodiment of the present invention illustrated in FIGURE 1 but in its assembled state;

FIGURE 3 is a schematic electrical circuit diagram illustrating the electrical connections of the embodiment of the present invention illustrated in FIGURES 1 and 2;

FIGURE 4 is a side elevational view of the invention shown in FIGURE 1; and

FIGURE 5 is a view similar to FIGURE 4 but'showing another embodiment of the invention.

Referring now to FIGURE 1, the draw-out switch-gear apparatus of the present invention comprises a fixed support structure shown generally at 10 and a removable frame assembly shown in exploded perspective view. The frame assembly comprises a front insulating wall 11 and a rear insulating wall 12 aligned generally in parallel spaced relationship and having connected therebetween a plurality of -fusible means such as the fuses at 13, 14, and 15. Also supported and connected between the rear insulating wall 12 and the front insulating wall 11 are a plurality of electrical conductors such as those shown at 16, 17, and 18. The fusible means 13, 14, and 15 are in electrical connection with a plurality of electrical connectors 19, 20, and 21 which pass through the front insulating wall 11 and are disposed in generally horizontal alignment thereon. Similarly, the plurality of electrical conductors 16, 17, and 18 are connected in electrical engagernent with a like plurality of electrical connectors disposed on the lower part of the front insulating wall 11, passing therethrough as shown at 22, 23, and 24. The electrical conductors 16, 17, and 18 are also connected at the rear insulating wall 12 to electrical connectors which pass therethrough and are disposed in hori zontal alignment along the rear insulating wall 12 as shown by the dash-line outlines at 25, 26, and 27. Ina like manner, electrical connectors (not shown) pass through the rear insulating wall 12 and are connected in electrical circuit with the fusible means 13, 14, and 15 and are aligned on the rear insulating wall 12 so as to be engageable with matching electrical connectors fixedly supported on the support structure 10.

The electrical connectors 19, 20, and 21 aligned on the top portion of the front insulating wall 11 and the like plurality of electrical connectors 22, 23 and 24 horizontally aligned on the lower portion of the front insulating wall 11 are disposed to receive and support in removable electrical engagement a circuit breaker such as that shown at 31, the circuit breaker being affixed to the plurality of aligned electrical connectors by suitable means such as the nuts shown at 32, 33, and 34. The front insulating wall 11 also carries suitable means such as the supports shown at 35, 36, 37, and 38 which are disposed and adapted to support a trim plate 39 to cover and protect the circuit breaker 31 and also provide a means by which the entire frame assembly may be slidingly moved back and forth on the support structure. The trim plate 30 carries two handle grips 40 and 41 for purposes of slidingly positioning the frame assembly. The trim plate 39 also has an aperture therein as shown at 42 which is configured, sized, and disposed so as to permit the positioning therethrough of the externally extending handle 43 of the circuit breaker 31 which is reciprocally operable between two positions of on and off commensurate with closed and open circuit conditions of the circuit in electrical connection with the draw-out switch-gear apparatus. The front and rear insulating walls 11 and 12 have afiixed therto a rail on each side such as that shown at 44, which rail is adapted to be slidingly engaged with an appropriately dimensioned, complementary rail member such as the rails 45 and 46 fixedly mounted on the support structure to receive the rails of the movable frame assembly. Thus, the entire frame assembly including the rails, the front and rear insulating walls, the electrically conductive elements connected and supported therebetween, the circuit breaker or other appropriate switch means and the trim plate are movably supported for sliding engagement within the fixed rails 45 and 46.

The fixed support structure comprises suitable, upright supports such as those shown at 47 and 48 which carry a fixed structure including a fixed wall member 48 generally vertically oriented and disposed so as to be parallel to the rear insulating wall 12 of the frame assembly. The fixed wall 48 carried by the support structure 10 has disposed thereon an array of electrical connectors such as are shown at 49, 50, 51, 52, and 53. These connectors are the so-called tulip-type and comprise a plurality of resilient, electrically conductive members such as those shown at 4911 disposed so that an electrical connector of the type carried by the rear insulating wall 12 of the frame assembly may be slidingly received in electrical contact therebetween; a resilient spring member such as that shown at 491: surrounds the plurality of resilient, electrically conductive members 49a so as to urge those members into positive electrical contact with the electrical connector when inserted slidingly therebetween. The tulip-type electrical connectors 49, 50, 51, 52, and 53 are aligned horizontally and disposed upon the fixed wall 48 of the support structure 10 so as to be slidably engageable in electrical contact with the like plurality of electrical connectors carried by the rear insulating wall 12 of the frame assembly of the apparatus. The electrical connectors carried in fixed, mounted position on the wall 48 are in turn arranged to be connectable to a source of electrical energy and an electrical load through suitable connecting means such as the electrically conductive straps shown at 54, 55, and 56 which are in electrical connection with and related to the tulip-type connectors 49, 50, and 51 respectively. Similar straps (not shown) are arrayed upon and carried by the plurality of electrical connectors of the tulip-type such as those shown at 52 and 53.

Referring now to FIGURE 2, the draw-out switchgear apparatus as embodied in FIGURE 1 is shown in its assembled state. The circuit breaker or other appropriate switch means 31 is shown as normally mounted in removable electrical connection with the plurality of electrical connectors carried by the front insulating wall 11 of the frame assembly. Immediately in front of the circuit breaker 31, a trim plate 39 is carried by its appropriate support means so as to permit the externally extending, reciprocally operable handle 43 to pass through the aperture 42 in the trim plate 39. The entire frame assembly is movably supported upon two horizontally disposed rails such as that shown at 44 and the complete frame assembly may be slidingly positioned forward and backward by means of the handles 40 and 41 disposed on the front trim plate 39. The rails of the frame assembly such as those shown at 44 are slidingly engaged with complementary type rails carried in fixed position by the support structure 10 such as the rail shown at 45. As was previously explained in connection with FIGURE 1, the tuliptype connectors carried by the fixed wall 48 are so disposed and arranged as to be aligned for engagement and electrical connection to the electrical connectors carried by the rear insulating wall 12 of the frame assembly of the apparatus. Thus, as shown in FIGURE 2, the movable frame assembly of the draw-out switch-gear apparatus is in its position of electrical engagement with the fixed support structure. The straps 54, 55, and 56 extending through the fixed wall 48 of the support structure 10 which, it will be recalled, are in electrical connection with tulip-type connectors 49, 50, and 51, respectively, are connected through suitable electrically conductive means such as that shown at 57, 58, and 59, respectively, to a source of electrical energy commonly referred to as the line, which in the illustration of FIGURE 2 takes the form of electrically conductive bus bars as shown at 60, 61, and 62. Similarly, the plurality of electrical connectors disposed along and passing through the rear insulating wall 12 and aligned horizontally on its lower portion are adapted to be engaged with a like array of aligned tulip-type connectors such as those shown at 52 and 53 of FIGURE 1, disposed in horizontal alignment on the fixed wall 48 of the support structure 10. Such connection is completed through appropriate electrically conductive means to an electrical load which typically may be a three-phase load, for example. Such electrical connections are shown in more detail in FIG- URE 3.

FIGURE 3, which is a schematic diagram of a typical electrical circuit including the draw-out switch-gear apparatus, carries numerical designations for elements of the actual structure as shown in FIGURES 1 and 2 though they are schematically represented in FIGURE 3. For clarity and simplicity in tracing the circuits, the line or source of electrical energy may be taken as the beginning of the multipole parallel circuits. As shown in FIGURE 3, line sources 60, 61, and 62 are electrically connected to the tulip-type connectors 49, 50, and 51, respectively, which in turn are in electrical connection with electrical connectors 28, 29, and 30, respectively, carried by the rear insulating wall 12 of the frame assembly. The connectors 28, 29, and 30 are also in electrical connection with the fusible means 13, 14, and 15, respectively, which are electrically connected with a like plurality of electrical connectors 19, 20, and 21, respectively, carried by the front insulating wall 11 of the frame assembly. The three electrical connectors 19, 20, and 21 are shown to be in electrical circuit connection with the circuit breaker 31 and furnish the electrical input thereto. The pairs of switch operated contact means which are relatively movable in respect to each other are schematically indicated within the circuit breaker 31 at 66; and, consistent with the on position of the externally extending, reciprocally operable handle 43 as shown, the relatively movable pairs of contacts 66 will be in the closed circuit condition completing the three circuits from the source of energy as connected to electrical connectors 19, 20, and 21 through the circuit breaker 31 and to the electrical connectors 22, 23, and 24, respectively, also carried by the front insulating wall 11 of the frame assembly. The electrical conductors 16, 17, and 18 are supported in alignment between the front insulating wall 11 and the rear insulating wall 12 where they are connected to electrical connectors 25, 26, and 27, respectively, carried by the rear insulating wall 12. As was previously explained in connection with FIGURES 1 and 2, the electrical connectors 25, 26, and 27 carried on the lower portion of the rear insulating wall 12 of the frame assembly are disposed to be engageable electrically with an array of similarly aligned tulip-type connectors 52, 53, and a third tulip-type connector (not shown in the perspective views of FIGURES 1 and 2 but designated at 27a in FIGURE 3). The plurality of tulip-type connectors 27a, 53, and 52 are connected through suitable electrical conductors 63, 64, and 65, respectively, to an electrical load to complete the three multi-pole parallel circuits from source to load.

In the illustrations of FIGURES 1, 2, and 3, a typical application of the draw-out switch-gear apparatus of the present invention may be in a three-phase installation of substantial current carrying capacity.

Referring again to FIGURE 3, it will be seen that when the externally extending, reciprocally operable handle 43 of the circuit breaker 31 is moved from the position illustrated to its reciprocal position as indicated by the dash-line outline of FIGURE 3, the relatively movable pairs of contacts 66 will be actuated to interrupt the flow of current through the circuit breaker and the three circuits with which it is in electrical connection by movement of the pairs of electrical contacts 66 to open the three circuits simultaneously.

As will be appreciated by those skilled in the art, the fusible means as shown at 13, 14, and afford a positive and reliable current limiting means, while the circuit breaker 31 provides an additional means responsive to the flow of overload currents therethrough to interrupt the circuits by automatically opening such circuits from their closed circuit condition to their open circuit condition.

In the form of the invention shown in FIGURE 5, a circuit breaker 70, of relatively smaller capacity is shown, having extended terminal straps 71 and 72, by which the breaker is mounted and connected to conductor studs 73 and 74 respectively. The studs 73 extend straight through between front and back spaced insulating plates 75, 76 and terminate in rear line terminal portions 77.

Three pairs of rigid conductive straps 78, 79 are also provided. The straps 78 each extend through the plate 75 and have a bent-over end 80, attached to the front surface of the front plate 75 by suitable means such as by screws, not shown. The straps 78' also have their opposite ends bent over at 81 and attached to the front surface of the rear insulating plate by screws 82. The straps 79 are similarly formed and attached to the front and rear plates 75, 76. The bent-over end 83 of each of the straps 79 supports a rear load terminal 84.

Three current-limiting fuses 85 are provided, each of which is connected between one of the straps 78 and a corresponding strap 79.

The load current path for each pole of the breaker 70 is therefore as follows: from breaker load terminal 72 to front load terminal 74 to a strap 78, through a fuse 85, to a strap 79, to rear load terminal 84. Suitable stationary sockets 86, 87 are provided to receive the terminals 77, 84.

The straps 78 and 79 are extended as described fully between the plates 75, 76, although this full length is not required for conducting purposes, for the purpose of providing adequate mechanical connection and support between the front and rear plates 75, 76.

It should be noted that, particularly as shown in the 6 perspective illustrations of FIGURES 1 and 2, the fusible means such as the fuses 13, 14, and 15 are arranged to be disposed in a generally upright or vertical disposition so that one fuse is spaced adjacent to one of the two insulating walls while the other two fuses are spaced adjacent the other insulating wall. Thus, fuses of considerable current carrying capacity and relatively large physical size may be fitted compactly into the frame assembly and circuit arrangement of the present invention.

Additionally, the arrangement by which the circuit breaker or other suitable switch means of the present invention may be readily removed from the frame assembly of the draw-out switch-gear apparatus of the present invention without removal of the entire movable assembly affords a most convenient means by which the circuit breaker or other switch means may be quickly replaced, repaired, calibrated or tested.

The embodiments of the present invention as illustrated in the drawings incorporate three-phase circuit breakers of the molded case type, but it will be apparent to those knowledgeable in the art that a disconnect or other switch means of suitable and appropriate type may be employed equally as well within the concept and spirit of the present invention.

While I have disclosed only certain embodiments of the invention, it will be readily appreciated that many modifications thereof may be made. I therefore intend, by the appended claims, to cover all such modifications as fallwithin the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Draw-out electrical switching apparatus comprising:

(a) a front insulating plate having a front and rear surface;

(b) a rear insulating plate having a front and rear surface;

(c) means rigidly interconnecting said front and rear insulating plates in parallel spaced relation to each other to form a draw-out frame assembly;

(d) a plurality of rear line terminals mounted on said rear surface of said rear insulating plate;

(e) a plurality of rear load terminals mounted on said rear surface of said rear insulating plate;

(f) a plurality of front line terminals mounted on said front surface of said front insulating plate;

(g) a plurality of front load terminals mounted on said front surface of said front insulating plate;

(h) a plurality of electrical conducting means between said front and rear insulating plates each interconnecting one of said front line terminals and a corresponding one of said rear line terminals by means extending through said front and rear insulating plates respectively;

(i) a plurality of electrical fuses supported between said insulating plates and each connected between one of said front load terminals and a corresponding one of said rear load terminals by conductive means extending through said front and rear insulating plates respectively,

(j) an electrical circuit control device mounted on said front surface of said front insulating plate and interconnected between said front line terminals and said front load terminals, and

(k) means carried by said frame assembly for slidably guiding said assembly for movement with respect to a relatively stationary support structure.

2. Draw-out electrical apparatus as set forth in claim 1 wherein:

(a) said front and rear insulating plates have corresponding opposed side edge portions;

(b) said means interconnecting said front and rear plates comprising a pair of rigid memrbers disposed adjacent said opposed side edge portions of said insulating plates respectively and each including at least one elongated guide surface extending substantially perpendicular to said front and rear plates for supporting and guiding said apparatus for movement generally perpendicular to the plane of said front and rear plates, and

(c) said rear line and said rear load terminals each comprising plug-in type electrical connecting means including means for making plug-in type engagement with corresponding stationary plug-in type terminals by movement in said direction perpendicular to said planes of said plates.

3. Draw-out electrical switching apparatus comprising:

(a) a front insulating plate having a front and rear surface;

(b) a rear insulating plate having a front and rear surface;

() means rigidly interconnecting said front and rear insulating plates in parallel spaced relation to each other to form a draw-out frame assembly;

(d) a plurality of rear line terminals mounted on said rear surface of said rear insulating plate;

(e) a plurality of rear load terminals mounted on said rear surface of said rear insulating plate;

(f) a plurality of front line terminals mounted on said front surface of said front insulating plate;

(g) a plurality of front load terminals mounted on said front surface of said front insulating plate; (h) a plurality of electrical conducting means between said front and rear insulating plates each interconnecting one of said front line terminals and a corresponding one of saidrear line terminals by means extending through said front and rear insulating plates respectively;

(i) said rear line terminals being substantially in alignment with corresponding ones of said front line terrninals;

(j) said rear load terminals being spaced a lesser distance from said rear line terminals than the spacing of said front load terminals from said front line terminals;

(k) a plurality of electrical fuses supported between said insulating plates and each connected between one of said front load terminals and a corresponding one of said rear load terminals by conductive means extending through said front and rear insulating plates respectively,

(1) said fuses each comprising an elongated tubular body member having terminals at first and second ends thereof, said fuses having their longitudinal dimension substantially parallel to said front and rear insulating plates and each having said first end terminal substantially in alignment with one of said front load terminals and having said second end thereof substantially in alignment with one of said rear load terminals, and

(in) means carried by said frame assembly for slidably guiding said assembly for movement with respect to a relatively stationary support structure.

4. Draw-out electrical switching apparatus comprising:

(a) a front insulating plate having a front and rear surface;

(b) a rear insulating plate having a front and rear surface;

(0) means rigidly interconnecting said front and rear insulating plates in parallel spaced relation to each other to form a draw-out frame assembly;

(d) a plurality of rear line terminals mounted on said rear surface of said rear insulating plate;

(e) a plurality of rear load terminals mounted on said rear surface of said rear insulating plate;

(f) a plurality of front line terminals mounted on said front surface of said front insulating plate;

(g) a plurality of front load terminals mounted on said front surface of said front insulating plate; (h) a plurality of electrical conducting means between said front and rear insulating plates each interconnecting one of said front line terminals and a corresponding one of said rear line terminals by means extending through said front and rear insulating plates respectively, said conducting means comprising a plurality of elongated rigid members fixedly connected to said front and rear insulating plates respectively;

(i) a plurality of electrical fuses supported between said insulating plates, rigid conductive means connecting said fuses each between one of said front load terminals and a corresponding one of said rear load terminals;

(j) whereby said rigid conducting means and said rigid conductive means provide mechanical spacing and supporting means between said insulating plates,

(k) an electrical circuit control device mounted on said front surface of said front insulating plate and interconnected between said front line terminals and said front load terminals, and

(1) means carried by said frame assembly for slidably guiding said assembly for movement with respect to a relatively stationary support structure.

5. Draw-out electrical switching apparatus comprising:

(a) a front insulating plate having a front and rear surface;

(b) a rear insulating plate having a front and rear surface;

(0) a pair of rigid guide rails rigidly interconnecting said front and rear insulating plates in parallel spaced relation to each other to form a draw-out frame assembly;

(d) a plurality of rear line terminals mounted on said rear surface of said rear insulating plate;

(e) a plurality of rear load terminals mounted on said rear surface of said rear insulating plate;

(f) a plurality of front line terminals mounted on said front surface of said front insulating plate;

(g) a plurality of front load terminals mounted on said front surface of said front insulating plate;

(h) a plurality of electrical conducting means between said front and rear insulating plates each interconnecting one of said front line terminals and a corresponding one of said rear line terminals by means extending through said front and rear insulating plates respectively;

(i) a plurality of electrical fuses supported between said insulating plates and each connected between one of said front load terminals and a corresponding one of said rear load terminals Iby conductive means extending through said front and rear insulating plates respectively,

(j) an electric circuit control device mounted on said front surface of said front insulating plate and interconnected between said front line terminals and said front load terminals, and

(k) said guide rails including portions for slidably guiding said draw-out frame assembly for movement with respect to a relatively stationary support structure.

No references cited.

BERNARD A. GILHEANY, Primary Examiner. 

1. DRAW-OUT ELECTRICAL SWITCHING APPARATUS COMPRISING: (A) A FRONT INSULATING PLATE HAVING A FRONT AND REAR SURFACE; (B) A REAR INSULATING PLATE HAVING A FRONT AND REAR SURFACE; (C) MEANS RIGIDLY INTERCONNECTING SAID FRONT AND REAR INSULATING PLATES IN PARALLEL SPACED RELATION TO EACH OTHER TO FORM A DRAW-OUT FRAME ASSEMBLY; (D) A PLURALITY OF REAR LINE TERMINALS MOUNTED ON SAID REAR SURFACE OF SAID REAR INSULATING PLATE; (E) A PLURALITY OF REAR LOAD TERMINALS MOUNTED ON SAID REAR SURFACE OF SAID REAR INSULATING PLATE; (F) A PLURALITY OF FRONT LINE TERMINALS MOUNTED ON SAID FRONT SURFACE OF SAID FRONT INSULATING PLATE; (G) A PLURALITY OF FRONT LOAD TERMINALS MOUNTED ON SAID FRONT SURFACE OF SAID FRONT INSULATING PLATE; (H) A PLURALITY OF ELECTRICAL CONDUCTING MEANS BETWEEN SAID FRONT AND REAR INSULATING PLATES EACH INTERCONNECTING ONE OF SAID FRONT LINE TERMINALS AND A CORRESPONDING ONE OF SAID REAR LINE TERMINALS BY MEANS EXTENDING THROUGH SAID FRONT AND REAR INSULATING PLATES RESPECTIVELY; (I) A PLURALITY OF ELECTRICAL FUSES SUPPORTED BETWEEN SAID INSULATING PLATES AND EACH CONNECTED BETWEEN ONE OF SAID FRONT LOAD TERMINALS AND A CORRESPONDING ONE OF SAID REAR LOAD TERMINALS BY CONDUCTIVE MEANS EXTENDING THROUGH SAID FRONT AND READ INSULATING PLATES RESPECTIVELY, 